Mandrills are a species of conservation concern and are important seed dispersers in their native central African forest habitat. However, most mandrill research has focused on captive populations, and little is known about their populations in the wild. We have extracted DNA from over one thousand fecal samples collected from wild groups (known as "hordes") in Lopé National Park (Gabon). We then use genetic tools to make inferences about past and future changes in mandrill population size, how mandrill "families" are structured, how often individuals move between hordes, and how females choose their mates. We have also done a deep dive into characterizing some of the genes controlling immunity in mandrills and other vertebrates--the major histocompatibility complex (MHC). Because the MHC is important to fitness, we can learn a lot about mandrill evolution by studying the genes encoding the MHC proteins.